High-performance liquid chromatography of biopolymers

The ability to separate biological macromolecules with good resolution on liquid chromatographic columns has depended on the development of suitable packing materials. In size exclusion chromatography, molecules are separated by size on the basis of differential permeation of the packing. Ion exchange, hydrophobic interaction (or reversed-phase), and affinity chromatography are all surface-mediated separation methods, although they depend on different retention mechanisms. High-performance liquid chromatographic columns designed for biopolymers offer major advantages over conventional columns in both speed and resolving power. The exponential growth of literature on the high-performance separation of peptides and proteins in particular indicates that the technique will become the dominant form of column liquid chromatography.     

Structure and properties of metallic glasses

Recent experience has shown that certain metal alloys can be put into glass form by rapid melt-quenching or by various condensation processes. Models for the nature and structure of these glasses are surveyed and shown to be quite parallel to those already developed for the more common nonmetallic glasses. The rather unique magnetic, superconducting, and mechanical properties and the technical potential of metallic glasses are also discussed.     

Motions and relaxations of confined liquids

When a liquid is confined in a narrow gap (as near a cell membrane, in a lubricated contact between solids, or in a porous medium), new dynamic behavior emerges. The effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates. These effects are more prominent, the thinner the liquid film. They appear to be the manifestation of collective motions. The flow of liquids under extreme confinement cannot be understood simply by intuitive extrapolation of bulk properties. Practical consequences are possible in areas from tribology and materials processing to membrane physics.     

Oxygen isotope constraints on the origin of impact glasses from the cretaceous-tertiary boundary

Laser-extraction oxygen isotope and major element analyses of individual glass spherules from Haitian Cretaceous-Tertiary boundary sediments demonstrate that the glasses fall on a mixing line between an isotopically heavy (delta(18)O = 14 per mil) high-calcium composition and an isotopically light (delta(18)O = 6 per mil) high-silicon composition. This trend can be explained by melting of heterogeneous source rocks during the impact of an asteroid (or comet) approximately 65 million years ago. The data indicate that the glasses are a mixture of carbonate and silicate rocks and exclude derivation of the glasses either by volcanic processes or as mixtures of sulfate-rich evaporate and silicate rocks.     

牛粪分离液与餐厨垃圾混合发酵试验参数优化

将牛粪固液分离处理,在分离液单独发酵基础上,添加不同比例餐厨垃圾连续发酵试验,考查各比例混合物料在不同水力停留时间下发酵性能,优化最佳配比、相应发酵工艺条件和参数。研究确定牛粪分离液和餐厨垃圾混合发酵适宜配比为7:3,HRT为25 d,获得VS甲烷产率226.67 m L CH_4·kg~(-1)VS,容积产气率1.20 L·L~(-1)·d-1,VS去除率达到47.94%。     

克鲁丝假丝酵母原生质体形成与再生条件的研究

研究了菌龄，酶浓度，酶作用时间，脱壁促进剂，渗透压稳定剂对克鲁丝假丝酵母（C.krus)原生质体形成与再生的影响，通过单因子试验，综合考虑形成率与再生率后，确定选用对数生长中期的菌体，以17%蔗糖为渗透压稳定剂，0.1%β-巯基乙醇进行预处理，2%蜗牛酶30℃作用60min为制备克鲁丝假丝酵母原生质体的最佳条件。     

黑曲霉原生质体形成与再生影响因子的研究

运用正交试验设计研究酶系统、酶解时间、酶解温度、渗透压稳定剂等因素对黑曲霉原生质体形成与再生的影响,确定黑曲霉原生质体形成与再生的最佳条件,获得高产原生质体,其浓度可达3.0×106个/mL,再生率达25%以上。并于欧林巴斯相差显微镜下观察了黑曲霉原生质体的形成过程。     

Rheology and microscopic topology of entangled polymeric liquids

The viscoelastic properties of high molecular weight polymeric liquids are dominated by topological constraints on a molecular scale. In a manner similar to that of entangled ropes, polymer chains can slide past but not through each other. Tube models of polymer dynamics and rheology are based on the idea that entanglements confine a chain to small fluctuations around a primitive path that follows the coarse-grained chain contour. Here we provide a microscopic foundation for these highly successful phenomenological models. We analyze the topological state of polymeric liquids in terms of primitive paths and obtain parameter-free, quantitative predictions for the plateau modulus, which agree with experiment for all major classes of synthetic polymers.     

美国花旗松离体胚愈伤组织诱导与茎芽分化的研究

以美国花旗松成熟胚为外植体进行离体培养诱导不定芽.试验和统计分析表明,在供试的MS、N6、SH、GD、WPM、DCR(改良)6种培养基中,DCR改良的培养基为花旗松芽诱导的最佳的初代培养基.DCR+6-BA2.0 mg/L是不定芽诱导的最佳组合,外植体不定芽诱导率达74,平均增殖系数为6,最大增殖率为8.NAA及2,4-D的添加均不利于芽的诱导;培养基中加入0.1的活性炭有利于不定芽的生长和伸长,但对不定芽的分化无显著的影响.     

Crystalline ordering in silica and germania glasses

The diffraction patterns of both silica and germania glasses are consistent with a structure in which nearly all of the atoms belong to tridymite-like regions of up to about 20 angstroms or more that are bonded efficiently together in a manner analogous to that found in twinned crystals.     

Packing structures and transitions in liquids and solids

Classification of potential energy minima-mechanically stable molecular packings-offers a unifying principle for understanding condensed phase properties. This approach permits identification of an inherent structure in liquids that is normally obscured by thermal motions. Melting and freezing occur through characteristic sequences of molecular packings, and a defect-softening phenomenon underlies the fact that they are thermodynamically first order. The topological distribution of feasible transitions between contiguous potential minima explains glass transitions and associated relaxation behavior.     

Lunar glasses and micro-breccias: properties and origin

Impact has been an important rock-forming process on the moon. Electron- and ion-probe analyses of major and minor elements show that most glasses and chondrule-like particles formed by shock melting of various proportions of mainly pyroxene, plagioclase, and ilmenite. This is the first direct evidence that chondrule-like molten droplets can form in impact events. Welding and shock lithification resulted in rocks texturally similar to chondrites but composition rules out the moon as source for chondrites. Impact craters on a nickel-iron sample evidence the importance of secondary impacts by accelerated lunar matter.     

Motions of molecules in liquids: viscosity and diffusivity

The fluidity of a simple liquid is proportional to its degree of expansion over the volume, V(0), at which its molecules are so crowded as to inhibit self-diffusion and viscous (as distinguished from plastic) flow. The equation of proportionality is 1/eta = B[(V - V(0))/V(0)] where eta is the viscosity and V is the molal volume. Values of B are the same for normal paraffins from C(3)H(8) to C(7)H(16) and then decrease progressively as the paraffin lengths increase. Values for other liquids, C(6)H(6), CCl(4), P(4), CS(2), CHCl(3), and Hg, appear to vary with repulsive forces. liquids can be moderately fluid when expanded by less than 10 percent; this shows the unreality of some theoretical treatments of the liquid state. Diffusivity begins from the temperature at which V equals V(0) and can be correlated for temperature dependence, and for solute-solvent interrelations.     

A topographic view of supercooled liquids and glass formation

Various static and dynamic phenomena displayed by glass-forming liquids, particularly those near the so-called "fragile" limit, emerge as manifestations of the multidimensional complex topography of the collective potential energy function. These include non-Arrhenius viscosity and relaxation times, bifurcation between the alpha- and beta-relaxation processes, and a breakdown of the Stokes-Einstein relation for self-diffusion. This multidimensional viewpoint also produces an extension of the venerable Lindemann melting criterion and provides a critical evaluation of the popular "ideal glass state" concept.     

毛泽东实事求是思想的形成和发展

实事求是是毛泽东思想的精髓。它是毛泽东以调查研究为基础，遵循理论与实践相统一的原则，把马克思主义在中国具体化的过程中逐步形成和发展起来的。     

芽胞杆菌来源沙奎那维的检测与分析

对阿氏芽胞杆菌Bacillus aryabhattai FJAT-14220发酵液中沙奎那维成分进行分析与检测。采用高效液相四级杆飞行时间质谱(liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry)分析阿氏芽胞杆菌FJAT-14220发酵液中胞外代谢物的成分。为获得代谢物的信息,首先采用MassHunter软件对原始数据进行分子特征提取,再通过Metlin数据库检索比对。在阿氏芽胞杆菌FJAT-14220发酵液中检测到883种代谢物,通过Metlin谱库搜索获得初步鉴定的有148种。其中,发现了具有生物活性的物质沙奎那维Saquinavir,其匹配得分达到93.08,占发酵液总代谢物相对含量的1.73%,保留时间为2.719 1 min,精确质量数为670.383 7。沙奎那维的发现为阿氏芽胞杆菌来源的多醚类抗生素的开发与利用提供理论依据。     

Synthesis and properties of metallic glasses that contain aluminum

The synthesis and properties of a class of metallic glasses containing up to 90 atomic percent aluminum are reported. The unusual formability of the glasses and their structural features are pointed out. Mechanical properties including tensile fracture strength and Young's modulus are reported along with crystallization temperatures. The unusually high strengths of the aluminum glasses can be of significant importance in obtaining high-strength low-density materials.     

Splashing of drops on shallow liquids

The events that follow the splashing of a drop on a liquid depend on the depth of the liquid. When the depth is less than about 5 millimeters the crown that is ejected is more unstable than that from a splash on a deep liquid. As the depth is decreased from 25 to 7 millimeters, there is an increase in the maximum height to which the Rayleigh jet rises, and in the number of drops that break away from the jet. With depths less than 7 millimeters these two quantities fall off sharply, and no jet drops are produced for depths less than about 3 millimeters.